iceweasel plugin

Where are iceweasel storing its plugins? And how to remove a plugin? Debian uses three directories to place plugins for iceweasel:

1. ~/.mozilla/plugins/
2. /usr/lib/mozilla/plugins/
3. /usr/lib/iceweasel/plugins/

Any plugin file or symbol link to plugin file in those directories is enabled plugin for iceweasel.

I do not know other guy's boxes, but in my box, disabling a plugin via the iceweasel tools menu can not succeed actually. You have to find the plugin file in the three directories mentioned above and move it out to other place in order to remove a plugin.